Contents In the pork industry, artificial insemination and the storage of boar semen in liquid at 17°C are routinely applied to optimize the ejaculate and bring about rapid genetic changes that are reflected in the animal protein. Although the results are satisfactory, they are below what occurs with natural mating. It is currently possible to preserve boar semen with storage at 17°C and slow freezing, since to date there is only one study on vitrification, with negative results applicable only in the case of implementing an intracytoplasmic sperm injection. In both methods and due to the sensitivity of boar sperm to osmotic and temperature changes, there is a loss in the quality of the initial sample; however, slow freezing in boar semen has greater deleterious effects on the sample that are reflected in the pregnancy rates and number of live births. Therefore, only 1% of all inseminations are done with frozen semen. The aim of this review is to provide advances and results of studies conducted on the preservation of boar semen, delving more deeply into the critical points that each of the preservation techniques presents, including bacterial contamination, extender components, temperature, ice nucleation, use of additives in extenders and the main deleterious effects on sperm quality.

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Pre‐treatment of boar semen with a red light photostimulation procedure increases its “in vivo” fertilising ability. However, “in vitro” conducted studies shown contradictory results regarding the ability of photostimulated spermatozoa to react against strong stress and to achieve the capacitation status. The aim here was to determine the effect of photostimulation on the response to short‐term moderate thermal stress of boar semen. Boar semen was exposed to red LED light regime emitting a 620–630 nm during 10 min of light, 10 min of rest and 10 min of light after 3 hr since semen was collected. An aliquot without photostimulation was included as a control. After the photostimulation, the sperm cells were incubated for 15 min at 37°C. Afterwards, motility, viability, intracellular Ca2+ level and production of reactive oxygen species (ROS) and peroxynitrite were analysed. The results showed that the photostimulated group maintained total motility throughout the time, whereas a significant decrease in total motility was observed in the nonphotostimulated control group. Furthermore, for kinetic parameters of motility, a significant increase was observed in LIN, STR and WOB in photostimulated spermatozoa. Peroxynitrite production was significantly increased in the photostimulated spermatozoa, whereas viability, ROS production and intracellular Ca2+ levels were not affected by photostimulation. In conclusion, photostimulation of commercial boar semen has a positive effect on motility of spermatozoa subjected to a short‐term moderate thermal stress, which was concomitant with an increase in peroxynitrite production.

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